I had placed a watch on Maciej's excellent 34c emulator a while back, and was just notified that now the price dropped to free. Then I noticed that all of his emulators are free right now. Act fast while you can get them! :)

This would for the models 21, 25, 33e, 34c, 35, 45, 55, 37e, 38c, 89, etc. There are a pile of them; I may have missed a couple models.

Here's a link to the 55 emulator. All the rest are listed on the "Related" page.